In the UK don't the laws say
Churches are banned (legally) from performing gay weddings for many years now?
http://www.independent.co.uk/news/u...ns-can-opt-in-for-gay-ceremonies-8405966.html
https://churchofengland.org/our-vie...he-church-of-england-an-explanatory-note.aspx
Anything that affected UK society that we can expect to play out in a similar fashion regarding that or are these countries too different to compare?
No, that's not what the laws say. As with everything else in the UK the law is way more complicated and ancient than that!
But very roughly, the same-sex marriage legislation in England and Wales gives the right (but not the duty) to marry same-sex couples to a few religions (Quakers and Jews I think) because these were specifically addressed in previous legislation. And that's not discriminatory, because they only have a right and not a duty to marry anyone at all.
The Church of England and the Church in Wales, as state-established churches, are in a strange legal position where normally they have a DUTY to marry those suitably qualified (for example, residing in the parish etc), and that duty has not been extended to the marriage of same-sex couples. The Church in Wales has been given the right to opt-in to same-sex marriage, but the Church of England hasn't been - but again that is because of historical legal stuff. In practice the Church of England can opt in if it so wishes - but that's subject to Canon Law of the Church (which because it is a State church also forms part of the law of England).
All
other churches (including Catholic, Muslim, Sikh, Orthodox etc etc) are, for the purposes of the Marriage Acts, merely buildings licensed for the performance of marriages, and as such they may perform same sex marriages subject to whatever the rules are for registering marriages.